Markertek also carries easy-to-use megaphones and portable public address systems from AmpliVox. Featuring powerful horns that are built to last, solid-state electronics, and an audience range up to 1 mile. These portable public address systems are perfect for directors working on expansive sets, or those who need to get their message across at large gatherings. Shop AmpliVox Portable Sound Systems and accessories at Markertek.